1. Field of the Invention
The present invention is directed generally to an arrangement for optically coupling light between an electro-optical transducer module and a light wave guide using two lenses.
2. Description of the Related Art
Electro-optical transducer modules are used for optical message transmissions, among other things. Transmission and/or receiver modules must be optically coupled to a light wave guide which is, for example, a monomode optical fiber transmission path.
It is known to use coupling optics between a monomode light waveguide and electro-optical components. Such coupling optics may include a first lens in front of a laser diode, which serves as a transmitter, and a second lens arranged in front of the light waveguide. The lenses and the optical fiber lie on an axis defined by the beam path of the laser diode.
The surfaces of such coupling optics act as mirroring, or at least partially reflective, surfaces which cause a back-reflection of a portion of the laser emission that causes disturbances in the light power and/or phase of the laser emission. As a result of such back reflection, the bit error rate in a message transmission system may be increased.
The back-reflection from the surfaces of the optical elements also occurs in receiver modules having an optical lens for optically coupling between the light waveguide fiber and, for example, a photodiode which serves as the receiver. The light reflections from this coupling optics can also disturb the laser.
The known measures for suppressing the disturbing back reflections using either an anti-reflection coating or an optical isolator are inadequate and also raise the costs of such arrangements.